Ceratopian Family Tree

Unlike sauropod or theropod lineages, there has generally been little
debate regarding the phylogeny of ceratopians. This is partially due
to the fact that these critters were fairly abundant in their day, and
that they left behind a strong fossil record. It has generally been
stated that the "holes" for this group are small by comparison. While
there are current debates about proper definitions for genera-level
taxonomy (i.e. lumping of several Triceratops skulls into one genus),
things tend to be fairly quiet above this level. However, I think a
strong case can be made for a higher-level phylogenic change.
Currently, the ceratopian lineage has been pretty straight forward:
Starting in the Early Cretaceous with the psittacosaurids, leading
into the Mid to Early-Late Cretaceous protoceratopids, and on up into
the Late Cretaceous Ceratopids. Sounding similar to a late-1800 model
for "evolutionary progress," it has been considered that a older
population was systematically replaced by an evolutionary
"breakthrough," with very little overlap in populations (with the
exception of co-existing Late Cretaeous protoceratopids and
ceratopids).
Recent fossil finds challange this arrangement. As I recently
discovered, an isolated ceratopian ulna was uncovered in an Early
Cretaceous deposit in Australia. Due to the existing timeline, this
ulna is considered to belong to a genus that belongs with the
psittacosaurids. The unusual thing about this ulna is that it bears a
striking resemblance to the Late Cretaceous protoceratopid,
Leptoceratops. Since Leptoceratops is considered to be a semi-bipedal
animal, and since this new psittacosaurid ulna is so similar to
Leptoceratops, then it can be concluded that Leptoceratops is better
classed as the only known Late Cretaceous psittacosaurid known at this
time. It can also be concluded that psittacosaurs existed throughout
the Cretaceous period, and through continual prospecting, we will
discover more psittacosaurid finds that will fill the gap between
Psittacosaurus and Leptoceratops.
Rob Meyerson
Orphan Vertebrate Paleontologist
***
"Strewth!"
-MPFC